Please start any new threads on our new site at https://forums.sqlteam.com. We've got lots of great SQL Server experts to answer whatever question you can come up with.

 All Forums
 General SQL Server Forums
 New to SQL Server Programming
 Unique Constraint

Author  Topic 

subbu_mareedu
Starting Member

11 Posts

Posted - 2014-06-02 : 06:08:48
Why we the Unique Constraint does'nt allow the multiple null values in Sql Server?

Can u tell me the Detailed reason about this?

Thanks & regards
Subbu.

subbu

robvolk
Most Valuable Yak

15732 Posts

Posted - 2014-06-02 : 06:57:49
That's the way SQL Server implemented the feature. The ANSI/ISO SQL standard permits multiple nulls, I'm assuming because their stance is that NULLs are never comparable and therefore never need to be compared for uniqueness. I personally don't agree with that and prefer SQL Server's implementation.

You can work around this in SQL Server 2008 or higher by using a filtered index.
Go to Top of Page

subbu_mareedu
Starting Member

11 Posts

Posted - 2015-03-03 : 01:35:50
Thanks Robvolk


subbu
Go to Top of Page
   

- Advertisement -